Process of preparing vinyl esters of organic acids



No Drawing.

Patented Dec. 30, 1930 UNITED STATES PATENT OFFICE HARRY B. DYKSTBA AND GARYL SLY, or WILMINGTON, DELAWARE, Assrenons 'ro E. I. no PON'J. DE NEMOURS & COMPANY, or WILMINGTON, DELAWARE, A coaroaa TION OF DELAWARE PROCESS OF PREPARING VINYL ESTERS OF ORGANIC ACIDS pared by the reaction of acetylene with the desired acid, but special precautions are necessary to secure the vinyl ester instead of the ethylidene ester. One way of accompllshing this is to use an excess of acetylene so that the efliuent gas stream will carry out the vinyl ester before it can react with more acid to give the ethylidene compound.

It has also been suggested that this could be accomplished by using a diluent which is an indifferent solvent, but the conditions necessary to be followed in order to obtain yields of commercial importance have not been known prior to our invention, so far as we are aware, and the best yields we have been able to obtain using the teaching of the prior art have been less than five per cent.

We have found, however, that if we use diluents Whose boiling point is above that of the acid employed, and between the boiling point of the acid and that of the corresponding ethylidene derivative in the case of acids of high boiling point, but above the boiling point of both the acid and the ethylidene compound with acids having low boiling points, the yield is many times greater. The line of demarcation between what is meant by acids of high boiling point and acids having low boiling points i' roughly 200 C. It is to be understood that this feature of the invention is not one which requires accurate determination.

It is therefore an object of this invention to provide a method of preparing vinyl esters.

It is another object of this invention to provide a method of preventing the formation of ethylidene esters in the preparation of vinyl esters.

With the above and other objects in view, which will be apparent as the description proceeds, We have set forth our invention in the following specification and have included the following examples by way of illustration and not as a limitation.

Application filed September 22, 1928. Serial No. 307,777.

Example 1 Acetylene in excess is passed into an autoclave containing a mixture of 2400 ams of glacial acetic acid, 328 grams of nely divlded mercuric sulfate, and 3600 ams of purified kerosene (b. p. 200275 (1.), accompanied by rapid mechanical stirring. The temperature is maintained at about 7075 C. When the rate of absorption decreases, which is in about 45 minutes with an active mercuric sulfate catalyst, the temperature is gradually raised in the course of 3 hours to about 90 0., the acetylene flow being continued in considerable excess. The distillate, carried over by the excess of acet-, ylene into' well cooled receivers, has a total weight of 900 to 1100 grams, from which 375 to 500 grams of vinyl acetate (b. p. 72-75" C.) may be separated in one distillation. This is a yield of 1115%, whereas the maximum yield obtained when no diluent was used was 2%. The residue in the autoclave is removed and the kerosene layer decanted for use in subsequent experiments. By our method the layer remaining after decantationof the kerosene may be distilled to secure acetic acid, acetic anhydride, and ethylidene dlacetate. Vinyl acetate is secured in higher yield and with a much sharper boiling range than with any previously known diluent, such as ligroin.

Example 2 Example 3 Acetylene in excess is passed for 3 hours, at a temperature of 1l5120 G. into a mixture of 100 grams of butyric acid, 13.6 grams of finely divided mercuric sulfate, and 200 urified kerosene, accompanied by high spec mechanical stirring. The distillate, amounting to about 80 grams, contains 18 grams of vinyl butyrate (b. p. 1l5-120 C.) giving a yield of 14% as compared with a yield of 4% which was secured when no diluent was employed.

' Although the above examples are limited to the use'of vinyl acetate, vinyl propionate and vinyl butvrate, the process set forth herein is applic. ble to the production of other vinyl esters, such as vinyl formate.

Although only kerosene and medicinal white oil have been specifically mentioned as diluents, we have investigated a variety of compounds, including triethylin (b. p. 18 185.5 C.), ethylene glycol m'onoethyl ether acetate (b. p. 154 C.) and high boiling gasoline (b. p. 150-180 (1.). However, we have found the aliphatic hydrocarbons to be superior from the 'points of non-reactivity and high solubility for acetylene. In the preparation of vinyl acetate, for example, we prefer to use kerosene, which has preferably been purified by treatment with fuming sulfuric acid, and which has a lower limit of 200 C. in its boiling range. Such a hydrocarbon is relatively insoluble in acetic acid and ethylidene diacetate and can be separated by decantation at the end of the run from the layer comprising these two liquids and used again without any intermediate purification.

While other catalysts may be used, we prefer to use mercuric sulfate, as this has been found to give the best results.

It will thus be apparent we have developed a new and useful method of preparing vinyl esters which permits the direct recovery of a high yield of the desired ester by a single distillation and, in the case of certain acids, such as acetic and formic, the separation of the residue by simple decantation to recover the major portion of the diluent, and the final separation of the residue left after decantation into its components.

As many apparently widely difierent embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that we do not limit ourselves to the specific embodiments thereof except as defined in the appended claims.

We claim:

1. The method of preparing vinyl esters of organic acids in improved yield, which comprises passing an excess of acetylene through an agitated charge of an organic acid heated to reaction temperature in contact with a catalyst and an aliphatic hydrocarbon distillate having a boiling point above that of the acid used.

2. The method of claim 1 in which the boiling point of the hydrocarbon derivative is also, above the boiling point of the ethylidene derivative of the acid grams of 3. The method of claim 1 in which the aliphatic hydrocarbon distillate is kerosene. 4. The method of claim 1 in which the acid is acetic acid and the diluent is kerosene, and in which the charge is agitated by rapid mechanical stirring while being heated to -7 5 C. Until the rate of absorption decreases, and then gradually raising the temperature to about 90 C. in the course of 3 hours.

In testimony whereof we aflix our signatures. V

HARRY B. DYKSTRA. CARYL SLY. 

